Search

The purpose of this article is to explore the amount of work, quantitated by flexion and extension cycles, that is needed to obtain a positive Elson test following a central slip injury.Thirteen frozen cadaveric fingers from individuals with an average age of 79.6 years were used. Testing was performed by imposing sinusoidal displacement of the 2 tendons, with loads ranging from 30 N to 2 N at 1 Hz. Following transection to the central slip, each finger was cycled 1,000 times using the same protocol adopted for the control. Following 100, 200, 300, and 1,000 cycles, we measured the extension angles of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints from the flexed position and the distance between landmarks of the extensor apparatus and simulated an Elson test.In both the fingers, the range of motion of the metacarpophalangeal and distal interphalangeal joints measured in the controls remained unchanged, whereas the range of motion of the proximal interphalangeal joint was significantly reduced immediately after central slip transection. Combining both ring and middle fingers, for a displacement of 5 mm, the force measured in the control (1.05 ± 0.69 N) increased to the value of 2.36 ± 0.97 N at the 1,000th cycle. Although the middle finger has shown a significant difference in force at 100 cycles following central slip transection, 200 cycles were needed to observe a difference on the ring finger.In controlled conditions, there is a variation in resistance to flexion of the distal interphalangeal joint. However, the amplitude of the forces is so small that they are likely imperceptible clinically. Delayed testing should be considered to increase the sensitivity of the test or in patients experiencing pain.Diagnostic V.

This article reviews a technique for arthroscopic fixation of an osteochondritis dissecans fragment with bone marrow aspirate concentrate augmentation. This technique involves safe harvest of bone marrow arthroscopically from the intercondylar notch, proper preparation and debridement of the parent bone, reduction of the progeny osteochondritis dissecans fragment, insertion of the bone marrow aspirate concentrate, and placement of multiple headless compression screws for fixation., Technique Video Video 1 Technique for arthroscopic fixation of osteochondritis dissecans (OCD) fragment of distal femur with bone marrow aspirate concentrate (BMAC) augmentation, highlighting how to safely harvest bone marrow arthroscopically and augment fixation of OCD fragment with BMAC.

Purpose To determine the ideal location for anterior cruciate ligament (ACL) suspensory cortical button placement on the lateral femur with the highest failure load and to establish the relationship of tunnel diameter and cortical thickness on load to failure. Methods Computed tomography (CT) data were obtained from 45 cadaveric distal femurs. A Cartesian coordinate system was established along the lateral femur with the lateral epicondyle (LE) as a reference point. Locations 0, 20 and 30 mm from the LE along lines 0°, 25°, 50°, and 75° posterioproximal from the axial plane were created. Tunnels connecting from each location to the center of the ACL footprint were simulated. Cortical thickness and long axis diameter of the oval cortical holes were determined for each location. Based on the CT data, custom drill guides were created and used to drill 4.5 mm tunnels at each lateral femur location to the ACL footprint on the cadaver femurs. Cortical buttons were placed at each location and pulled using a servohydraulic testing system. The correlation of tunnel diameter and cortical thickness to button failure load were analyzed using a regression analysis. Results Significant differences were found for failure load (P

Temporary external fixation has been widely utilized in the stabilization of plateau fractures while waiting for an optimization of the soft tissue conditions before subsequent permanent internal fixation. Simultaneously, MRI is beneficial in the assessment of concomitant damage to ligaments and menisci so that these injuries could be promptly identified, and surgical planning executed at the time of definitive fixation of the bony injury. Increasing numbers of side-bars and pins have been previously suggested to increase frame rigidity, but at the same time, several studies have indicated the presence of MRI artifacts which may obscure key anatomical structures, even when MRI-compatible fixation devices are used. This study aims to identify, among six potential configurations, the construct that maximizes stability while most minimizing the number of MRI artifacts generated among different configurations commonly used.There is one or more configurations among the others that maximize stability while preserving a clinically acceptable level of MRI quality.Six constructs were recreated on cadaveric specimens and identified by the disposition of the bars: H, Anterior, Flash, Hashtag, Rhomboid, and Diamond. Stage one evaluated the amount of artifact produced during MRI on instrumented cadaveric legs, as well as the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) at five specific regions of interest. Stage two assessed the amount of compressional and torsional stiffness of the configurations on bone surrogate models.Image artifacts were not detected within the knee joint for all considered constructs. In terms of SNR The H, Anterior, Hashtag, and Diamond configurations were not significantly different from their control (p0.366) while the others were significantly different (p0.03). The values of CNR found for the H and Hashtag configurations were not significantly different from their controls (p0.07) while the remaining configurations were significantly different (p0.03). In compression, the H and Diamond configurations had similar stiffness (p=0.468) of 35.78N/mm and 31.44N/mm, respectively, and were stiffer than the other configurations. In torsion, the constructs have shown different stiffness (p0.001) with a minimum value of 0.66 Nm/deg for the Rhomboid configuration, which was significantly less stiff than the Anterior configuration (1.20 Nm/deg [p0.001]). There was no difference between the Diamond and H configurations (p=0.177) or between them and the Hashtag configuration (p=0.215).An external fixator construct directly bridging the femur and tibia without interconnections is the most stable and produces MRI scans without image artifacts that would interfere with diagnostic quality.V, basic science study, diagnostic imaging and mechanical testing.

Pelvic external fixation using anterosuperior pins provides a quick method of stabilization without necessitating fluoroscopic guidance. Various locations, depths, and inclinations have been cited for external fixator pins; however, the existing literature lacks clear indications for the angular difference between pins. Thus, we aimed to determine the greatest degree of sagittal pin spanning angulation (SPSA) between two iliac crest pins and how intraosseous depth (ID) affects these angulations. A newly developed computer algorithm produced cross sections of 3D pelvic reconstructions in the sagittal plane in 5° increments. Computer-generated pins with IDs of 60, 75, and 90 mm were positioned in 5° increments transversely. Pins were assessed for cortical containment to define values for SPSA and transverse pin spanning angulation (TPSA). A bimodal distribution revealed varying degrees of insertion frequency and SPSA, cranially and caudally. The caudal distribution exhibited greater cortical containment with larger values for SPSA and TPSA. The highest insertion frequency (85.7%) and largest SPSA (155°) were observed for the 60-mm ID. Increasing ID resulted in further bony penetration and smaller values for SPSA and TPSA. Expanding the degree of SPSA between inserted pins in anterosuperior pelvic external fixation can be challenging due to the thinning of the iliac wing, which affords a narrow corridor for intraosseous pin containment. An ID of 60 mm allows larger degrees of SPSA while maintaining higher rates of cortical pin containment when compared to pins with greater IDs.

To evaluate Workers' Compensation (WC) patients who underwent arthroscopic shoulder surgery for workplace shoulder injuries and to determine whether there was an association between earlier return to light duty and earlier return to full duty.After receiving institutional review board approval, we performed a retrospective chart review of all WC patients treated with shoulder arthroscopic surgery by 2 senior authors between 2011 and 2018. The patients were divided into 2 groups: Group 1 went back to light-duty work within the first 100 days after surgery, whereas group 2 performed light-duty work after 100 days or performed no light-duty work. The primary outcomes included the length of time from surgery to light-duty work and the length of time from surgery to return to the full-duty work level.A total of 59 patients met the inclusion criteria. There was a moderate correlation between the number of days at which the patients were released to light duty and the days they were able to be released to full duty (Earlier return to light duty is associated with earlier return to full duty after shoulder arthroscopic surgery in patients with a Workers' Compensation claim. Additionally, WC patients who returned to early light duty in the first 100 days postoperatively had a higher rate of return to full duty than did patients who did not return to early light duty.Level III, case-control study.

Objective To compare radius of curvature (RoC) of distal femur osteochondral autograft transfer (OAT) donor sites from the intercondylar notch and trochlear ridge with recipient sites on the distal and posterior condyles and evaluate differences between recipient sites. Design Nineteen cadaveric femurs were scanned with a 3-dimensional high-resolution sensor. Donor regions included the lateral (LTR) and medial trochlear ridges (MTR), and the lateral (LICN) and medial intercondylar notch (MICN). Recipient regions analyzed were the distal medial (DMFC), posterior medial (PMFC), distal lateral (DLFC), and posterior lateral femur condyle (PLFC). Six-millimeter OAT grafts were simulated, and average RoC of all regions was compared using an analysis of variance. Post hoc testing was performed using Fisher’s least significant difference. Results We found no significant differences in RoC of the LICN compared with all 4 recipient sites ( P = 0.19, 0.97, 0.11, and 0.75 for DLFC, PLFC, DMFC, and PMFC, respectively) or the LTR and MTR to the posterior condyles (LTR vs. PLFC and PMFC; P = 0.72, 0.47, MTR vs. PLFC and PMFC P = 0.39, 0.22, respectively). Significant differences were found for RoC of the MICN compared with each recipient site ( P < 0.001) and between distal and posterior femoral condyles (DLFC vs. PLFC, P = 0.016; DMFC vs. PMFC, P = 0.023). Conclusion The LICN is the ideal donor option for all recipient sites on the femoral condyles with respect to RoC of 6-mm OAT plugs. The MTR and LTR were acceptable donor sources for the posterior condyles, while the MICN was a poor match for all recipient sites. Additionally, the distal femur condyle and posterior femur condyle have different RoCs.

Pelvic internal fixation has become a popular method for treatment of unstable pelvic ring injuries. Although successful, one complication is femoral nerve palsy from compression of the connecting rod. In light of this complication, this study was designed to evaluate sagittal inclinations of the rod and the feasibility of using a rod with a constant curvature.It is hypothesized that that there is a connection between the sagittal inclination of the rod and the rod to bone distance, as well as single rod can be contoured with a constant curvature to be used in the majority of all patients.Three dimensional models of pelvis CTs from a single level 1 trauma center were created and imported into a program where software superimposed a pre-contoured rod in the sagittal planes upon the pelvic slices. The sagittal inclination was deemed acceptable is no interference occurred between the area of compression risk and the rod. For each pelvis and considered sagittal rod inclination, the rod radius of curvature (ROC), minimal rod to bone distance (RTB) and transverse inclinations (φThe sagittal inclinations feasible for all subjects were between 15° to 30°. In this sagittal range, the average RTB varied in values ranging from 4.0±0.9mm to 25.4±11.4mm (p0.01). Only 46% of subjects allowed a rod with constant curvature.Our study found that a rod to bone distance of 15mm was not safe for all models. As well, many subject models did not allow placement of pre-contoured rod. Patient specific templating of pelvic subcutaneous internal fixation is strictly needed to limit complications.VII; Basic Science.

INTRODUCTION Urgent treatment of septic arthritis is key in preventing devastating morbidity or mortality. Accurate diagnosis is critical, and the standard diagnostic cutoff of 50,000 synovial leukocytes may be altered by previous administration of antibiotics. Our objective was to identify and compare a cutoff synovial leukocyte count with a high sensitivity and specificity for diagnosis of septic arthritis in patients who received antibiotics and those who had not. A receiver operating characteristic (ROC) curve was used to provide a discriminate cutoff value for diagnosing septic arthritis. METHODS A retrospective chart review of 383 patients was done over a 13-year period including those who had arthrocentesis of any joint. Two groups were created, those who had not been given antibiotics within 2 weeks (control) and those who received intravenous or oral antibiotics within 2 weeks before arthrocentesis. Relevant data included synovial leukocyte count and differential cell count. Additional metrics included temperature, erythrocyte sedimentation rate, and C-reactive protein. A ROC curve determined the optimal synovial white blood cell cutoff for diagnosing septic arthritis in native joints for each group. RESULTS The ROC curve determined that patients who received antibiotics had an optimal cutoff of >16,000 cells (sensitivity = 82%, specificity = 76%), and a neutrophil percentage cutoff of >90% (sensitivity = 73%, specificity = 74%). The control group had an optimal synovial leukocyte cutoff of >33,000 cells (sensitivity = 96%, specificity = 95%). The optimal neutrophil percentage cutoff in the control group was >83% neutrophils (sensitivity = 89%, specificity = 79%). CONCLUSION When a patient is given antibiotics before arthrocentesis, a diagnostic value of >16,000 synovial leukocytes should be used to guide treatment of septic arthritis. A diagnostic value of >33,000 synovial leukocytes yields the highest accuracy for diagnosis of septic arthritis in patients who have not been given antibiotics before arthrocentesis. LEVEL OF EVIDENCE III.

Case We report a case of a right knee lateral bucket-handle meniscal tear repair in a 25-year-old woman bilateral below-knee amputee. At the 4-year follow-up, the patient was ambulatory in a prosthesis with a successful outcome. Conclusion Meniscus repair in below-knee amputees requires careful evaluation and surgical management. Specific consideration should be given to evaluating limb alignment, maintaining the stump integrity, surgical technique, modified bracing, and rehabilitation. This case report demonstrates that bucket-handle meniscus repair can be successful in a below-knee amputee.

The novel coronavirus pandemic, also known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has placed an immense strain on healthcare systems across the entire world. Consequently, multiple federal and state governments have placed restrictions on hospitals such as limiting "elective surgery" and recommending social or physical distancing. We review the literature on several areas that have been affected including surgical selection, inpatient care, and physician well-being. These areas affecting inpatient paradigms include surgical priority, physical or social distancing, file sharing for online clinical communications, and physician wellness. During this crisis, it is important that orthopaedic departments place an emphasis on personnel safety and slowing the spread of the virus so that the department can still maintain vital functions. Physical distancing and emerging technologies such as inpatient telemedicine and online file sharing applications can enable orthopaedic programs to still function while attempting to protect medical staff and patients from the novel coronavirus spread. This literature review sought to provide evidence-based guidance to orthopaedic departments during an unprecedented time. Orthopaedic surgeons should follow the Centers for Disease Control and Prevention guidelines, wear personal protective equipment (PPE) when appropriate, have teams created using physical distancing, understand the department's policy on elective surgery, and engage in routines which enhance physician wellness.

Pelvic external fixation using anterosuperior pins provides a quick method of stabilization without necessitating fluoroscopic guidance. Various locations, depths, and inclinations have been cited for external fixator pins; however, the existing literature lacks clear indications for the angular difference between pins. Thus, we aimed to determine the greatest degree of sagittal pin spanning angulation (SPSA) between two iliac crest pins and how intraosseous depth (ID) affects these angulations.A newly developed computer algorithm produced cross sections of 3D pelvic reconstructions in the sagittal plane in 5° increments. Computer-generated pins with IDs of 60, 75, and 90 mm were positioned in 5° increments transversely. Pins were assessed for cortical containment to define values for SPSA and transverse pin spanning angulation (TPSA).A bimodal distribution revealed varying degrees of insertion frequency and SPSA, cranially and caudally. The caudal distribution exhibited greater cortical containment with larger values for SPSA and TPSA. The highest insertion frequency (85.7%) and largest SPSA (155°) were observed for the 60-mm ID. Increasing ID resulted in further bony penetration and smaller values for SPSA and TPSA.Expanding the degree of SPSA between inserted pins in anterosuperior pelvic external fixation can be challenging due to the thinning of the iliac wing, which affords a narrow corridor for intraosseous pin containment. An ID of 60 mm allows larger degrees of SPSA while maintaining higher rates of cortical pin containment when compared to pins with greater IDs.

Background: Magnetic Resonance Imaging (MRI) allows orthopaedic surgeons to assess Osteochondritis Dissecans (OCD) of the distal femur in children. When surgical fixation is indicated, headless compression screws can be used to stabilize the fragment and allow it to heal. During screw placement it is important to make sure the screw is not too long or it may cross the physis, leading to physeal growth arrest. Hypothesis/Purpose: The purpose of the study was to determine the optimal screw length for osteochondritis dissecans fixation of the pediatric distal femur. A secondary objective was to compare the thickness of the epiphysis of the pediatric distal femur at different locations and screw trajectories. Methods: This retrospective, IRB-approved, single-institution study identified 113 pediatric patients (ages 6-17 years old) with a knee MRI from January 1, 2008 to January 1, 2020. A total of 6 measurements were obtained on each pediatric MRI by two residents. The longitudinal axis of the femur was used as a reference trajectory. Three measurements were obtained from medial femoral condyle and lateral femoral condyle, respectively. The lengths measured were from the anteromedial (AM), posteromedial (PM), and distalmedial (DM) on the medial femoral condyle to the physis. On the lateral femoral condyle, the anterolateral (AL), posterolateral (PL), and distallateral (DL) were measured. 2 sample t-testing, chi-square analysis, and Pearson’s correlation coefficient were utilized to find significant associations. Results: Of the 113 pediatric knees identified, 32 did not meet inclusion criteria, yielding 81 patients for final analysis. The average epiphyseal thickness of the bone was 25.5 mm ± 4.2 (CI 24.5 – 26.4, range 14.1 – 33.1). There was a difference in epiphyseal thickness based on screw trajectory () with the average thickness being 23.0, 22.2, 30.5, 29.3, 25.5, and 22.3 mm for the AM, AL, PM, PL, DM and DL respectively. There was a negative correlation between increasing age and epiphyseal cartilage thickness (). There was a positive correlation between increasing age and bone only epiphyseal thickness (). Conclusion: Our study outlines important measurements that orthopedic surgeons must be aware of when operating on OCD lesions in pediatric patients. These results can aid in determining the appropriate screw length that can be implanted into the pediatric distal femur to avoid damaging the distal femur. Our study results show that the optimal screw length to use in pediatric OCD lesion is 18mm in order to avoid physeal disturbance in the majority of pediatric patients. [Figure: see text][Figure: see text]

Background Newer repair techniques of anterior cruciate ligament tears, including augmentation with internal brace, have shown promising clinical results. Few biomechanical studies exist comparing anterior cruciate ligament repair only versus repair with internal brace. The purpose of this study was to compare the load to failure and stiffness of anterior cruciate ligament repair with internal brace augmentation versus repair-only. Methods Proximal femoral avulsion type anterior cruciate ligament injuries were created in 20 cadaver knees. Anterior cruciate ligament repair-only or repair with internal brace was performed using arthroscopic tools. Load to failure and failure modes were collected, with calculations of stiffness and energy to failure performed. Findings The average load to failure for the internal brace group was higher than the repair-only group: 693 N (SD 248) versus 279 N (SD 91), P = .002. The stiffness and energy to failure values were higher for the internal brace group than the repair-only group: 83 N/mm versus 58 N/mm, P = .02 and 16.88 J (SD 12.44) versus 6.91 J (SD 2.49), P = .04, respectively. Failure modes differed between groups (P = .00097) with 80% failure in the repair-only due to suture pull through the anterior cruciate ligament and 90% failure in the internal brace group due to suture button pull through the femur. Interpretation There was higher load to failure, stiffness, and energy to failure for the internal brace group compared to the repair-only group, and a high positive correlation between bone density and load to failure for the internal brace group. Clinical significance Anterior cruciate ligament repair with internal brace augmentation demonstrates significantly higher load to failure. It may be a useful adjunct to protect the anterior cruciate ligament repair from failure during the early stages of healing.

Introduction Temporary external fixation has been widely utilized in the stabilization of plateau fractures while waiting for an optimization of the soft tissue conditions before subsequent permanent internal fixation. Simultaneously, MRI is beneficial in the assessment of concomitant damage to ligaments and menisci so that these injuries could be promptly identified, and surgical planning executed at the time of definitive fixation of the bony injury. Increasing numbers of sidebars and pins have been previously suggested to increase frame rigidity but, at the same time, several studies have indicated the presence of MRI artifacts which may obscure key anatomical structures, even when MRI-compatible fixation devices are used. This study aims to identify, among six potential configurations, the construct that maximizes stability while most minimizing the number of MRI artifacts generated among different configurations commonly used. Hypothesis There is one or more configurations among the others that maximize stability while preserving a clinically acceptable level of MRI quality. Material and methods Six constructs were recreated on cadaveric specimens and identified by the disposition of the bars: H, anterior, flash, hashtag, rhomboid, and diamond. Stage one evaluated the amount of artifact produced during MRI on instrumented cadaveric legs, as well as the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) at five specific regions of interest. Stage two assessed the amount of compressional and torsional stiffness of the configurations on bone surrogate models. Results Image artifacts were not detected within the knee joint for all considered constructs. In terms of SNR The H, anterior, hashtag, and diamond configurations were not significantly different from their control (p > 0.366) while the others were significantly different (p 0.07) while the remaining configurations were significantly different (p Discussion An external fixator construct directly bridging the femur and tibia without interconnections is the most stable and produces MRI scans without image artifacts that would interfere with diagnostic quality. Level of evidence V, basic science study, diagnostic imaging and mechanical testing.

In pelvic fractures, dysfunction of the pelvic ring is often stabilized with supra-acetabular pin insertion. In existing literature, there are heterogeneous indications on proper pins selection and inclinations. Therefore, this study aimed to quantify the narrowing of safe pin corridors in the transverse and sagittal planes with increments of intraosseous screw depths. A computer algorithm created cross-sections over three-dimensional pelvic reconstructions at sagittal inclinations from 45° cranial to 45° caudal in 5° increments. Templates of screw depths spanning 60-120 mm in 15 mm increments were disposed in the transverse plane from 45° medial to 45° lateral. Each intraosseous screw depth and transverse angle were evaluated for intraosseous containment to evaluate ranges narrowing with increasing screw depths. The 60-mm depth resulted in the largest sagittal range (60.9° ± 6.9°) and transverse range (27.5° ± 4.1°) at 30° caudal. Increasing depths by 15 mm resulted in ranges being significantly different from one another (p < 0.01). The sagittal plane of 20° cranial had the highest frequency of insertion for all depths, while transverse ranges were narrowed (p < 0.01). Bisecting angles were similar for sagittal planes 20° cranial to 30° caudal with an average of 27.9° ± 1.2° (p ≥ 0.115). In conclusion, while 60 mm depths can be inserted with the highest discretion, 15 mm increments in depth significantly reduce safe ranges. Screws depths above 90 mm have low frequencies of insertion, should be inserted more cranially and must be considered prone to breaching. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1790-1797, 2019.

BackgroundThe soft tissue structures surrounding the human knee joint have been the subject of extensive anatomic study. The detailed histologic findings within the bone of the human patella, however, have not been systematically studied. While the nerves supplied to the periarticular soft tissues have been very well documented, the nerves supplied to the interior of the bony patella have never been described.HypothesisThis study tests the hypothesis that the patella contains an intraosseous nerve network. Further, the authors investigate the anatomic location of these intraosseous nerves to better understand their possible clinical relevance.Study DesignDescriptive laboratory study.MethodsTen matched pairs of cadaveric patellae (left and right patellae from the same individual; 20 total) were prepared for evaluation by hematoxylin and eosin staining using a technique that allows the creation of complete, large histologic sections of individual patellae. The matched specimens were dissected free of soft tissue and then sectioned using a diamond-wafering saw into 3-mm sagittal (left patella) and transverse (right patella) sections. Sections were then decalcified and whole-mounted into paraffin blocks for further sectioning using a large-format microtome. All 20 specimens were prepared for evaluation. Age at death averaged 80 years (range, 64-91). All specimens demonstrated at least grade II chondromalacia.ResultsNineteen of 20 (95%) specimens demonstrated intraosseous nerves. Of 248 sections studied, 116 (47%) demonstrated intraosseous nerves, with 227 individual nerves identified. The density of intraosseous nerves was greatest in the medial and central portions of the patella, with a significant paucity identified laterally.ConclusionThe primary intraosseous innervation of the patella derives from a medially based neurovascular bundle.Clinical RelevanceA better understanding of the nerves within the human bony patella may improve understanding the patho-physiology of anterior knee pain syndromes.

We discuss the use of an optical correlator with a highly coupled filter and dappled targets to track an object in a field of view cluttered by background noise and/or similar objects. The dappled targets are fractal images whose statistics are independent of scale. Each is unique for tracking the targets. We report the drop in correlation (hence recognition) of an object as a function of in-plane rotation and as a function of range. We discuss plans for an application in Johnson Space Center's Automation and Robotics group, in which correlation processing of these targets would distinguish an object and pass its position and orientation to a robot control system. Using MEDOF (minimum Euclidean distance optimal filter) to create filters on the coupled filter modulator, we show that background clutter can be optically filtered out.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We previously reported computer code designed to generate optical correlator filters by putting our optimization algorithm into practice. This code is MEDOF: Minimum Euclidean Distance Optimal Filter. MEDOF's version 1.0 demonstrated filters which maximize correlation peak intensity (INT). We also gave some discussion to the quadratic ratio metrics of signal to noise ratio (SNR) and peak to correlation energy ratio (PCE). These advanced metrics are now functional in the second version of MEDOF, which is publicly available through NASA's software distribution channel, COSMIC. This paper focuses on some of the practical issues faces when using MEDOF to generate filters. The underlying mathematical principles of MEDOF are discussed in passing while providing references to sources of more theoretical detail.

We use color for visual presentation of certain effects that are complex in nature but have previously been shown using only amplitude display. In particular we show (1) the field that results from complex encoding of an input object, and (2) the departure from ideal of the object that is actually correlated with the input object. The departures are caused by limitations of filter SLMs and by the algorithms that compute filters for them.

We show laboratory results showing coupled-filter improvements in certain correlator performance metrics: signal to noise ratio, peak correlation energy, and peak to total energy. We had previously shown improvements in correlation intensity. The filters were built using JSC computer code for minimum Euclidean distance optimal filters.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report a computer code that affects several efficiencies in taking a recently developed filter optimization algorithm into practice. The algorithm (Richard D. Juday, `Optimal realizable filters and the minimum Euclidean distance principle,' Applied Optics, in press) analytically optimizes filters on arbitrary modulators (coupled, binary, full complex, fractional 2(pi) phase, etc.). Its quadratic ratio metrics include intensity, signal to noise, and peak to correlation energy. The user supplies necessary information to the program, and also certain common complex arithmetic functions. The code is to be available from COSMIC under the name `MEDOF -- Minimum Euclidean Distance Optical Filters,' NT control number MSC-22380.

Optical correlators used in pattern recognition should have their operation optimized according to physically measurable behavior related to the correlator's task. The optimization is best done with explicit consideration of the limited set of complex values available to the filter. We earlier developed a theoretical filter computing strategy, MEDOF (minimum Euclidean distance optimal filter), that optimizes a wide variety of correlation metrics on physically realistic modulators. We use a single reference image and add noise according to a stated model. We show laboratory results for filters optimizing a variety of metrics on a highly coupled SLM. The results show improvements in the metrics by using MEDOF when compared with some other filter computing strategies such as matching phase. Optimizing SNR appears preferable to the other metrics when detecting an object in clutter of known power spectral density. © 1999 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(99)01802-4)